The principal functions of the Clinical Core of the UCI ADRC are: to recruit, characterize, and longitudinally follow subjects as part of our clinical and neurobiological investigations of aging and Alzheimer's disease, and to provide a resource for all investigators involved in the study of aging and AD at UCI and nationally by providing well-characterized subjects for clinical trials, genetic studies, tissue repositories, and imaging protocols. With this renewal the Clinical Core has responded to the RFA and the needs of our investigators by assembling three cohorts of subjects to examine the cognitive states associated with old age and Down syndrome. Extending our previous cohort of subjects (the Clinical Cohort, N=250), the Core has added two special interest groups of subjects. The 90+ Autopsy Cohort (N=100) provides unique opportunities to better understand the brain/behavior relationships and effects of aging in the most rapidly growing segment of the population, the oldest old. Our center also brings to the ADC system another unique cohort, the adult Down Syndrome Cohort (N=75). These subjects are followed with the same methodology used for all ADRC subjects, and provide opportunities for innovative investigations by our basic and clinical scientists. Brain donation is requested from all ADRC subjects, and is required on enrollment, except for DS subjects (50% autopsy participation) and minorities. We aggressively work to increase autopsy participation in these subjects. The Clinical Core, with expertise in neurology, neuropsychology, and nursing, interacts closely with all ADRC cores, NACC, and local and national researchers. Supporting the ADRC's experimental studies, the Clinical Core provides subjects and clinical data to Project 1, biological tissues and clinical data to Project 2, and human data for comparison studies in the transgenic investigations of Project 3. With our unique subject populations, the ADRC Clinical Core brings to UCI and the ADC system a central resource for innovative studies of aging and AD.